1. Field of the Invention
The present invention relates to a communication apparatus for efficiently multiplexing and communicating a plurality of types of data such as real-time data such as speech data for which real-time transmission is required and non-real-time data such as LAN data for which a certain delay is allowed, a communication system, and a control method for the apparatus and system.
2. Description of the Related Art
A multimedia communication system capable of communicating various types of data generally uses a means for transmitting real-time data such as multiplexed data of speech data and the like in a PBX (private branch exchange) and a non-real-time data in a LAN or the like, for which a certain delay is allowed, by time division multiplexing (TDM) or the like. Recently, a means for transmitting data upon dynamically allocating a band by using a statistical multiplexing effect is available.
According to this means using the statistical multiplexing effect, non-real-time data is divided into blocks each having a fixed frame length, and each fixed-length block is formed as a frame to be transmitted. When a request to transmit real-time data is generated while the non-real-time data frames are transmitted, the real-time data is inserted between the fixed-length block frames.
This system may use a simple method in which when real-time data is generated while variable-length transfer information requested as non-real-time data is transmitted, transmission of the real-time data is started immediately after transmission of the non-real-time data, which is currently transmitted, is complete.
When, however, the above TDM scheme is used, it is difficult to effectively use a band, because the band is ensured even while no data is transmitted.
In the scheme of dynamically allocating a band, while fixed-length blocks are transferred, real-time-data is inserted between the fixed-length blocks. Frame control codes and the like are inserted in units of fixed-length blocks, resulting in an increase in overhead. This makes it difficult to effectively use the band.
In contrast to this, if the fixed length of each block is increased for effective use of a band, the start of the transfer of real-time data from this transfer state is delayed, resulting in an increase in delay in data transfer.
In addition, in the simple method in which when real-time data is generated while variable-length transfer information requested as non-real-time data is transmitted, the transmission of the real-time data is started immediately after the transmission of the non-real-time data is complete, the start of the transfer of the real-time data from this transfer state is delayed depending on the data length of the non-real-time data. As a consequence, data transfer may be greatly delayed.
It is an object of the present invention to effectively use bands.
It is another object of the present invention to efficiently communicate non-real-time data and real-time data.
It is still another object of the present invention to communicate real-time data without degrading the real-time property even during communication of non-real-time data.
According to the present invention, the foregoing object is attained by a communication apparatus for transferring, to a communication network, a frame formed by multiplexing real-time data for which real-time transmission is required and non-real-time data for which a certain delay is allowed, upon dynamically allocating a band by using a statistical multiplexing effect, comprising detection means for detecting generation of the real-time data, disassembly means for disassembling the non-real-time data into at least one fixed-length data packet, frame generating means for generating the frame from the disassembled data packet or the real-time data, insertion means for, when generation of the real-time data is detected by said detection means while the frame is generated by using the disassembled data packet, interrupting the generation of the frame using the disassembled data packet, and inserting generation of the frame using the real-time data, and resuming means for, after the insertion is performed by said insertion means, resuming the generation of the frame using the disassembled data packet before the insertion.
In accordance with the present invention as described above, when a request to transfer real-time data is generated while non-real-time data is transferred, the non-real-time data is transferred in units of frames each having a predetermined data length, and the real-time data frame is inserted between the non-real-time data frames. Thereafter, the remaining data packets are continuously transferred, thereby effectively using a band.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.